KR102537696B1 - Soc management apparatus of energy storage device, and method therefor - Google Patents

Abstract

Applied to the DC microgrid according to an embodiment of the present invention, in the energy storage system including at least one energy storage device, the SoC management device for managing the state of charge (SoC) of each energy storage device The SoC management method may include receiving, by the SoC management device, an SoC of a connected energy storage device; calculating, by the SoC management device, an offset voltage based on the received SoC; and performing, by the SoC management device, droop control based on the offset voltage and a fixed droop coefficient to perform SoC balancing of the connected energy storage devices.

Description

Remaining capacity management device and method of energy storage device {SOC MANAGEMENT APPARATUS OF ENERGY STORAGE DEVICE, AND METHOD THEREFOR}

The present invention relates to an apparatus and method for managing the remaining capacity of an energy storage device, and in an energy storage system in which a plurality of energy storage devices are linked to a DC microgrid, SoC (State Of Charge) based offset voltage of each energy storage device and a device and method for controlling SoC balancing by performing droop control based on a fixed group coefficient.

As interest in renewable energy such as photovoltaic power generation is rapidly increasing, research and development on DC microgrid and energy storage system (ESS) for efficient energy management are being actively conducted.

On the other hand, if the energy consumption of the DC microgrid increases, the capacity of the existing energy storage system must also be expanded. In order to expand the capacity of the energy storage system, it is possible to consider replacing the existing energy storage system, but this is uneconomical. Therefore, it is possible to consider a method of expanding the capacity of the energy storage device by installing an additional energy storage device in the existing facility. According to this method, a plurality of energy storage devices can be configured in conjunction with the DC microgrid.

When a plurality of energy storage devices are linked and operated, overdischarge and overcharge of a specific energy storage device may occur due to SoC (State Of Charge) imbalance. Since overdischarge and overcharge of the energy storage device is a factor that shortens the lifespan of the energy storage device, it must be operated within the SoC tolerance range. In order to solve these problems, balancing control is required so that each energy storage device operates with the same SoC as much as possible within the SoC tolerance range.

A droop control technique has been proposed for SoC balancing of energy storage devices in existing DC microgrids. Existing droop control techniques are representative of a method of changing a droop coefficient based on SoC and a method of adding a control command to reduce SoC errors between a plurality of energy storage devices using communication. The method of changing the droop coefficient reduces the circulating current and performs SoC balancing operation by changing the droop coefficient according to the SoC state, but when the droop coefficient is converted by the SoC, the voltage stability of the distribution network becomes unstable. . The method of adding a control command to reduce SoC errors between multiple energy storage devices using the following communication does not affect the voltage stability of the distribution network, but if communication is disconnected due to external factors, SoC balancing is not performed. Therefore, the reliability and stability of the DC microgrid are deteriorated.

In order to solve the above problems, according to an embodiment of the present invention, a system capable of performing SoC balancing operation between a plurality of energy storage devices by controlling the charge/discharge current through an offset value in which the SoC is reflected without using communication, and provides a way

Applied to the DC microgrid according to an embodiment of the present invention in order to achieve the above object, the remaining capacity (State Of Charge; SoC) of each energy storage device in the energy storage system including at least one energy storage device An SoC management method of a SoC management device that manages, the SoC management device comprising the steps of receiving an SoC of a connected energy storage device; calculating, by the SoC management device, an offset voltage based on the received SoC; and performing, by the SoC management device, droop control based on the offset voltage and a fixed droop coefficient to perform SoC balancing of the connected energy storage devices.

The calculating of the offset voltage may include calculating an offset voltage proportional to a difference between the nominal voltage and the output voltage and inversely proportional to a difference between a maximum allowable value and a minimum allowable value of SoC.

The step of calculating the offset voltage according to an embodiment may include calculating the offset voltage in consideration of an AC system and a charge/discharge operation mode within a range of a minimum allowable value and a maximum allowable value of the SoC of the energy storage device. .

The AC system and charging and discharging operation modes according to an embodiment include a first operation mode in which the load is greater than the amount of power generation and in a discharged state, a second operation mode in which the amount of power generation is in a charged state while the amount of power generation is greater than the amount of load, and the amount of power generation is greater than the load and discharged It is characterized in that it is divided into a third operation mode, which is a state, and a fourth operation mode, which is a charging state while the load is greater than the amount of power generation.

According to an embodiment, in the calculating of the offset voltage, as the first operation mode progresses and SoC decreases, the y-intercept of the droop curve approaches the output voltage of the energy storage device and the discharge current decreases, It is characterized in that an offset voltage that sets the discharge current to 0 is calculated when the SoC reaches the minimum allowable value of the SoC.

According to an embodiment, in the step of calculating the offset voltage, as the second operation mode progresses and SoC increases, the y-intercept approaches the output voltage of the energy storage device and the charging current decreases, but the SoC is SoC It is characterized in that the offset voltage is calculated to set the charging current to zero when the maximum allowable value of is reached.

According to an embodiment, in the step of calculating the offset voltage, the y-intercept of the droop curve is formed to be higher than the output voltage in the third operation mode, and when the SoC reaches the maximum allowable value of the SoC, the nominal voltage and the output voltage The discharge operation proceeds based on a value twice the error of , and when SoC reaches the minimum allowable value of SoC, an offset voltage that sets the discharge current to 0 is calculated.

According to an embodiment, in the step of calculating the offset voltage, the y-intercept of the droop curve in the fourth operation mode is formed lower than the output voltage, and the charging current is set to 0 when the SoC reaches the maximum allowable value of the SoC. It is characterized in that for calculating the offset voltage to.

Applied to a DC microgrid according to another embodiment of the present invention, the SoC management device for managing the state of charge (SoC) of each energy storage device in an energy storage system including at least one energy storage device is , an input unit for receiving the SoC of the energy storage device; and a control unit for calculating an output voltage of the connected energy storage device by the SoC management device calculating an offset voltage based on the received SoC and performing droop control based on the offset voltage and a fixed droop coefficient. It is characterized in that it includes.

According to an embodiment of the present invention, using a fixed droop coefficient, SoC balancing of a plurality of energy storage devices is achieved without affecting the voltage stability of the distribution network.

In addition, according to an embodiment of the present invention, it is possible to extend battery life by preventing overdischarge and overcharge by operating within an SoC allowable range.

In addition, since only the SoC of each energy storage device is used in a non-communication method, the stability and reliability of microgrid operation can be improved by reducing communication dependence.

1 is a conceptual diagram showing the configuration of a DC microgrid to which an apparatus for managing the remaining capacity of an energy storage device according to an embodiment of the present invention is applied.
2 is a block diagram for explaining a droop control operation of an apparatus for managing remaining capacity of an energy storage device according to an embodiment of the present invention.
3 is a diagram for explaining a first operation mode according to an embodiment of the present invention.
4 is a diagram for explaining a second operation mode according to an embodiment of the present invention.
5 is a diagram for explaining a third operation mode according to an embodiment of the present invention.
6 is a diagram for explaining a fourth operation mode according to an embodiment of the present invention.
7 is a block diagram showing the configuration of an apparatus for managing remaining capacity of an energy storage device according to an embodiment of the present invention.
8 is a flowchart illustrating a method for managing remaining capacity of an energy storage device according to an embodiment of the present invention.
9 is a graph showing simulation verification results of a first operation mode and a second operation mode according to an embodiment of the present invention.
10 is a graph showing simulation verification results of a charge/discharge switching operation according to an embodiment of the present invention.
11 is a graph showing simulation verification results of a third operation mode and a fourth operation mode according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals have been used for like elements throughout the description of each figure.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

1 is a conceptual diagram showing the configuration of a DC microgrid to which an apparatus for managing the remaining capacity of an energy storage device according to an embodiment of the present invention is applied.

The DC microgrid includes an Interlinking Converter (ILC) (10) connected to the AC grid, a PV DC/DC converter (20) connected to a photovoltaic generator (PV), a load DC/DC converter (30) connected to a load, It includes a bidirectional DC/DC converter 40 connected to the energy storage device, and each component is connected in parallel.

An interlinking converter (ILC) 10 applies droop control to stably operate the power distribution network through power supply and regeneration operations.

Distributed power applied to the DC microgrid according to an embodiment uses photovoltaic power generation and uses a P&O algorithm for maximum output follow-up control (MPPT).

Here, the load is a constant power load (CPL, Constant Power Load), and the energy storage device is 2 units as an example, but is not limited thereto.

Each of the plurality of energy storage devices performs SoC balancing control by applying the SoC-based offset droop control technique by the remaining capacity management device described in FIGS. 2 to 5 in order to maintain the same SoC as much as possible without departing from the SoC tolerance range. .

2 is a block diagram for explaining a droop control operation of an apparatus for managing remaining capacity of an energy storage device according to an embodiment of the present invention.

The remaining capacity management device 100 performs droop control by applying an offset considering the SoC of each energy storage device.

Droop control described in an embodiment of the present invention is performed as shown in Equation 1 based on a fixed droop coefficient R _d and an offset ΔV _offset formed considering SoC.

[Equation 1]

Here, the offset voltage ΔV _offset is set in consideration of the operation mode of the AC system and energy storage device that may appear during microgrid operation.

The operation mode is divided into a total of four modes, and is divided into a charge/discharge mode of the energy storage device when the amount of power generation by renewable energy is lower than the load amount and a charge/discharge mode of the energy storage device when the amount of power generation is higher than the load amount. That is, the operation modes include a first operation mode in which the load is greater than the amount of power generation and in a discharged state, a second mode in which the amount of power generation is greater than the load and in a charged state, a third mode in which the amount of power generation is greater than the load and in a discharged state, and a load greater than the amount of power generation It is divided into the fourth operation mode, which is large and in a charged state.

3 is a diagram for explaining a first operation mode according to an embodiment of the present invention. FIG. 3(a) is a diagram for explaining energy flow in the first operation mode, and FIG. 3(b) is a diagram showing changes in the droop curve in the first operation mode.

Referring to (a) of FIG. 3, in the first operation mode, the energy storage system (ESS) performs a discharging operation and supplies power to the distribution network through the interlinking converter (ILC) 10 in the AC system, so that energy is It can be seen that it flows toward the load through the load DC/DC converter 30.

Referring to (b) of FIG. 3 , since the generation amount is lower than the load amount in the first operation mode, the voltage V _ESS of the energy storage system (ESS) is formed lower than the nominal voltage V _nom . In addition, as the operation progresses in the first operation mode, the SoC of each energy storage device (ESS) decreases due to the discharging operation, and the offset voltage ΔV _offset at this time is calculated by Equation 2.

[Equation 2]

Here, SoC _max is the maximum allowable voltage of the SoC, SoC _min is the minimum allowable voltage of the SoC, and SoC means the output voltage of the SoC.

As shown in Equation 2, as the SoC of the energy storage device (ESS) is discharged, when the SoC is SoC _max , the offset voltage is 0, and the discharge operation is performed, and when the SoC decreases from SoC _max to SoC _min , ΔV _offset increases, the y-intercept of the droop graph approaches the output voltage and the discharge current decreases. When SoC becomes SoC _min , the offset voltage becomes maximum and the discharge current of the energy storage device (ESS) is limited to zero.

If the initial SoC of each energy storage device is formed differently, SoC balancing is performed without an additional communication line because a module with a high SoC is discharged with a large output current and a module with a low SoC is discharged with a small output current according to each SoC.

In addition, when SoC reaches SoC _min , ΔV _offset is calculated so that the y-intercept of the droop graph becomes the same value as the output voltage V _out . Accordingly, the discharge current is limited to 0 even without an additional circuit breaking algorithm to prevent overdischarge. As such, even if the discharge current of the energy storage device is limited to 0, since the power distribution network voltage is controlled through the interlinking converter (ILC) 10 in addition to the energy storage device, operation is possible within the grid voltage tolerance range.

4 is a diagram for explaining a second operation mode according to an embodiment of the present invention. FIG. 4(a) is a diagram for explaining energy flow in the second operation mode, and FIG. 4(b) is a diagram showing a droop curve change in the second operation mode.

Referring to (a) of FIG. 4, in the second operation mode, the energy storage system (ESS) performs a charging operation, and in the AC system, a power regeneration operation is performed through an interlinking converter (ILC) 10, and a photovoltaic generator It can be seen that power is supplied to the power distribution network by the PV DC/DC converter 20 connected to the PV, and energy flows toward the load through the load DC/DC converter 30.

Referring to (b) of FIG. 4 , since the generation amount is higher than the load amount in the second operation mode, the voltage V _ESS of the energy storage system (ESS) is formed higher than the nominal voltage V _nom . In addition, as the operation progresses in the second operation mode, the SoC of each energy storage device (ESS) is charged and increased over time, and the offset voltage ΔV _offset at this time is calculated by Equation 3.

[Equation 3]

Here, SoC _max is the maximum allowable voltage of the SoC, SoC _min is the minimum allowable voltage of the SoC, and SoC means the output voltage of the SoC.

As shown in Equation 3, when SoC becomes SoC _min , the offset voltage becomes 0 and the charging operation is performed with the maximum charging current, and as the SoC of the energy storage device (ESS) is charged, the SoC approaches SoC _max . As ΔV _offset increases, the y-intercept of the droop graph approaches the output voltage V _out and the charging current decreases. When SoC becomes SoC _max , the y-intercept becomes equal to V _out and the charging current of the energy storage device (ESS) is limited to 0.

Similar to the first operation mode, since each ESS limits the charging current based on the SoC, SoC balancing is naturally performed between each ESS, and when the SoC reaches SoC _max , the charging current is limited to 0 to prevent overcharging.

In general, the operation mode of the DC microgrid is mainly performed by the first operation mode and the second operation mode described above. However, since the amount of power generation is additionally greater than the amount of load, the energy storage device must perform a charging operation, but more power must be regenerated through the AC system. In this case, the energy storage device should perform a discharging operation rather than a charging operation. In addition, there is a case in which the energy storage device needs to perform a discharging operation because the amount of power generated is smaller than the amount of load, but requires a charging operation because the SoC is low. In this case, the energy storage device must perform a charging operation. That is, an operation mode in which power directions of the energy storage device and the AC system are reversed will be described below with reference to FIGS. 5 and 6 .

5 is a diagram for explaining a third operation mode according to an embodiment of the present invention. FIG. 5(a) is a diagram for explaining energy flow in the third operation mode, and FIG. 5(b) is a diagram showing changes in the droop curve in the third operation mode.

Referring to (a) of FIG. 5, in the third operation mode, the energy storage device (ESS) performs a discharging operation, and in the AC system, a power regeneration operation is performed through an interlinking converter (ILC) 10, and a photovoltaic generator It can be seen that power is supplied to the power distribution network by the PV DC/DC converter 20 connected to the PV, and energy flows toward the load through the load DC/DC converter 30.

Referring to (b) of FIG. 5 , although the generation amount is higher than the load amount in the third operation mode, in order for the energy storage device to discharge, the voltage V _ESS of the energy storage device (ESS) is formed higher than the nominal voltage V _nom . In addition, in order for the energy storage device to perform a discharge operation in the third operation mode, the y-intercept of the droop graph must be higher than V _ESS , and the offset voltage ΔV _offset at this time is calculated by Equation 4.

[Equation 4]

Here, SoC _max is the maximum allowable voltage of the SoC, SoC _min is the minimum allowable voltage of the SoC, and SoC means the output voltage of the SoC.

As shown in Equation 4, when the SoC of the energy storage device (ESS) is SoC _max , the discharging operation proceeds based on the value of ΔV _offset twice the error between _Vnom and _Vout . Accordingly, the discharge current is reduced by the offset. When the SoC of the energy storage device (ESS) reaches SoC _min , the y-intercept of the droop curve coincides with V _out by the offset, and the discharge current is limited to 0 to prevent overdischarge. Similar to the mode described above, in the third operation mode, even if the initial SoC of each energy storage system (ESS) is formed differently, the SoC balancing operation is performed because the offset is formed based on the SoC.

6 is a diagram for explaining a fourth operation mode according to an embodiment of the present invention. FIG. 6(a) is a diagram for explaining energy flow in the fourth operation mode, and FIG. 6(b) is a diagram showing changes in the droop curve in the fourth operation mode.

Referring to (a) of FIG. 6, in the fourth operation mode, the energy storage system (ESS) performs a charging operation and supplies power to the power distribution network through an interlinking converter (ILC) 10 in the AC system, and solar light It can be seen that power is supplied to the power distribution network by the PV DC/DC converter 20 connected to the generator (PV), and energy flows toward the load through the load DC/DC converter 30.

Referring to (b) of FIG. 6 , in the fourth operation mode, although the generation amount is lower than the load amount, in order for the energy storage device (ESS) to perform a charging operation, the voltage V _ESS of the energy storage device (ESS) is lower than the nominal voltage V _nom is formed When the SoC of the energy storage device (ESS) is SoC _min , it is charged with the maximum current at the voltage V _ESS of the energy storage device (ESS), and the offset voltage ΔV _offset at this time is calculated by Equation 5.

[Equation 5]

The charging current of the energy storage device (ESS) decreases over time by ΔVoffset according to Equation 5, and when SoC reaches SoCmax, the y-intercept is the same as the voltage V _ESS of the energy storage device (ESS) value and the charging current is limited to 0 to prevent overcharging.

In a plurality of ESSs, a small charging current flows when the SoC is high, and a large charging current flows when the SoC is low, so that SoC balancing between the plurality of ESSs is achieved.

Autonomous mode switching is possible through the sign of the error between V _nom and V _out in a non-communication manner by the first to fourth operation modes described above.

7 is a block diagram showing the configuration of an apparatus for managing the remaining capacity of an energy storage device according to an embodiment of the present invention, and FIG. 8 is a diagram for explaining a method for managing the remaining capacity of an energy storage device according to an embodiment of the present invention. It is a flow chart.

FIG. 7 is an apparatus for managing remaining capacity of an energy storage device according to an embodiment of the present invention, which is applied to FIGS. 1 and 2 described above. When applied to FIG. 1 , the remaining capacity management device 100 may be provided for each energy storage device (ESS). Alternatively, it may be provided before or after the bidirectional DC/DC converter.

Referring to FIGS. 7 and 8 , the input unit 110 of the apparatus 100 for managing the remaining capacity of an energy storage device according to an embodiment of the present invention receives the SoC measurement value of the connected energy storage device in step S110. The input unit 110 transfers the input SoC measurement value to the controller 120 .

In step S120, the controller 120 of the device 100 for managing remaining capacity calculates an offset voltage based on the received SoC measurement value.

The control unit 120 calculates the offset voltage in consideration of the AC system and charge/discharge operation mode within the range of the minimum and maximum values of the SoC of the energy storage device, and the offset voltage is proportional to the difference between the nominal voltage and the output voltage , in inverse proportion to the difference between the maximum and minimum values of the SoC.

The controller 120 determines the generation amount, the load amount, and the charge/discharge operation mode, and calculates the offset voltage according to a pre-stored equation for each mode.

Equations stored in advance are the same as those included in the operation mode described with reference to FIGS. 3 to 6 .

In step S130, the control unit 120 of the remaining capacity management device 100 performs droop control based on the calculated offset voltage and a fixed droop coefficient to perform SoC balancing of the connected energy storage devices.

The remaining capacity management method applied to the DC microgrid according to an embodiment of the present invention controls the charge/discharge current according to the SoC state, thereby achieving the effect of SoC balancing between a plurality of energy storage devices having different initial SoCs. You can get it. In addition, even without an additional circuit-breaking algorithm, the energy storage device can prevent overdischarge and overcharge by limiting the charge/discharge current at the boundary of the SoC tolerance range by the residual capacity management method.

Unlike conventional SoC-based droop control, which affects the grid voltage stability by changing the droop coefficient, the method for managing remaining capacity according to an embodiment of the present invention uses SoC-based offset without changing the droop coefficient. The effect of the above operation can be obtained without affecting the grid voltage stability. In addition, unlike other prior art techniques for achieving SoC balancing using communication, the method for managing remaining capacity according to an embodiment of the present invention uses only the SoC of each energy storage device in a non-communication manner, so communication dependence is low, and microcontroller You can see the effect of increasing reliability in grid operation.

9 is a graph showing simulation verification results of a first operation mode and a second operation mode according to an embodiment of the present invention.

For the simulation of the remaining capacity management method of the energy storage device, two energy storage devices were adopted, and the initial SoC of each energy storage device was set differently.

Referring to (a) of FIG. 9, it is possible to check the current change of the charging and discharging operation of the energy storage device in the first operation mode according to the amount of power generation and the amount of load, and referring to (b) of FIG. 9, the amount of power generation And the energy storage device in the second operation mode according to the size of the load can check the current change of the charging and discharging operation. As the charge/discharge operation proceeds in the first operation mode and the second operation mode, the magnitude of the charge/discharge current changes according to the SoC. It can be confirmed that the energy storage device of low SoC flows a small discharge current and SoC balancing operation is performed. In addition, it can be confirmed that the charge/discharge current converges to 0A at the boundary of the SoC tolerance range. This prevents overcharge and overdischarge problems.

10 is a graph showing simulation verification results of a charge/discharge switching operation according to an embodiment of the present invention.

Figure 10 (a) shows the current change from the discharge mode to the charge mode, Figure 10 (b) shows the current change from the charge mode to the discharge mode.

As can be seen with reference to FIG. 10 , autonomous mode switching is possible even when there is a change in load amount, and during mode switching, the grid voltage is maintained within an allowable range.

11 is a graph showing simulation verification results of a third operation mode and a fourth operation mode according to an embodiment of the present invention.

Referring to (a) of FIG. 11, it is possible to check the current change of the charging/discharging operation of the energy storage device in the third operation mode according to the amount of power generation and the amount of load, and referring to (b) of FIG. 11, the amount of power generation And the energy storage device in the fourth operation mode according to the size of the load can check the current change of the charging and discharging operation.

As can be seen with reference to FIG. 11, although the generation amount is greater than the load amount in the third operation mode of FIG. is the case 11(b) shows a case in which the amount of power generation is smaller than the amount of load in the fourth operation mode, but according to Equation 5, the energy storage device performs a charging operation and performs a power supply operation in the AC system. It can be seen that in the third operation mode and the fourth operation mode, similarly to the first operation mode and the second operation mode of FIG. 9, SoC balancing is performed and the operation is performed within the SoC tolerance range. Therefore, according to an embodiment of the present invention, overdischarge and overcharge problems do not occur in any mode.

The above description is merely an example of the technical idea of the present invention, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments implemented in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed according to the claims below, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

Claims (16)

In the SoC management method of a SoC management device that is applied to a DC microgrid and manages the state of charge (SoC) of each energy storage device in an energy storage system including at least one energy storage device,
The SoC management device receiving the SoC of the connected energy storage device;
calculating, by the SoC management device, an offset voltage based on the received SoC; and
performing, by the SoC management device, droop control based on the offset voltage and a fixed droop coefficient to perform SoC balancing of the connected energy storage devices;
Including,
In the step of calculating the offset voltage,
An offset voltage is calculated in consideration of the AC system and charge/discharge operation mode within the range of the minimum and maximum values of the SoC of the energy storage device,
The AC system and charge/discharge operation mode,
The first operation mode in which the load is greater than the amount of generation and discharged; the second operation mode in which the amount of generation is greater than the load and in a charged state; the third mode in which the amount of generation is greater than the load and in a discharged state It is divided into a fourth operation mode, which is
In the step of calculating the offset voltage,
As the first operation mode progresses and SoC decreases, the y-intercept of the droop curve approaches the output voltage of the energy storage device and the discharge current decreases, but when SoC reaches the minimum allowable value of SoC, the discharge current is set to 0 A method for managing the remaining capacity of an energy storage device that calculates an offset voltage to
According to claim 1,
In the step of calculating the offset voltage,
A method for managing remaining capacity of an energy storage device, characterized in that the offset voltage is calculated in proportion to the difference between the nominal voltage and the output voltage of the energy storage device and inversely proportional to the difference between the maximum allowable value and the minimum allowable value of the SoC.
delete delete delete According to claim 1,
In the step of calculating the offset voltage, as the second operation mode progresses and SoC increases, the y-intercept approaches the output voltage of the energy storage device and the charging current decreases, but SoC reaches the maximum allowable value of SoC In the case of, the remaining capacity management method of the energy storage device, characterized in that for calculating the offset voltage that sets the charging current to zero.
According to claim 1,
In the step of calculating the offset voltage, in the third operation mode, the y-intercept of the droop curve is formed higher than the output voltage, and when the SoC reaches the maximum allowable value of the SoC, a value twice the error between the nominal voltage and the output voltage A method for managing remaining capacity of an energy storage device, characterized in that the discharge operation proceeds based on and calculates an offset voltage that sets the discharge current to zero when SoC reaches the minimum allowable value of SoC.
According to claim 1,
In the step of calculating the offset voltage, when the y-intercept of the droop curve is formed lower than the output voltage in the fourth operation mode and the SoC reaches the maximum allowable value of the SoC, the offset voltage which sets the charging current to 0 is calculated. Remaining capacity management method of the energy storage device, characterized in that.
In the SoC management device applied to the DC microgrid and managing the remaining capacity (State Of Charge; SoC) of each energy storage device in an energy storage system including at least one energy storage device,
an input unit for receiving the SoC of the energy storage device connected to the SoC management device; and
The SoC management device calculates an offset voltage based on the received SoC, and the SoC management device calculates an output voltage of the connected energy storage device by performing droop control based on the offset voltage and a fixed droop coefficient;
Including,
The control unit,
An offset voltage is calculated in consideration of the AC system and charge/discharge operation mode within the range of the minimum and maximum values of the SoC of the energy storage device,
The AC system and charge/discharge operation mode,
The first operation mode in which the load is greater than the amount of generation and discharged; the second operation mode in which the amount of generation is greater than the load and in a charged state; the third mode in which the amount of generation is greater than the load and in a discharged state It is divided into a fourth operation mode, which is
The control unit,
As the first operation mode progresses and SoC decreases, the y-intercept of the droop curve approaches the output voltage of the energy storage device and the discharge current decreases, but when SoC reaches the minimum allowable value of SoC, the discharge current is set to 0 Remaining capacity management device of an energy storage device that calculates an offset voltage to
According to claim 9,
The control unit,
An apparatus for managing remaining capacity of an energy storage device, characterized in that for calculating an offset voltage proportional to the difference between the nominal voltage and the output voltage of the energy storage device and inversely proportional to the difference between the maximum allowable value and the minimum allowable value of the SoC.
delete delete delete According to claim 9,
The control unit,
As the second operation mode progresses and SoC increases, the y-intercept approaches the output voltage of the energy storage device and the charging current decreases, but when the SoC reaches the maximum allowable value of the SoC, the offset setting the charging current to 0 Remaining capacity management device of the energy storage device, characterized in that for calculating the voltage.
According to claim 9,
The control unit,
In the third operation mode, the y-intercept of the droop curve is formed higher than the output voltage, and when the SoC reaches the maximum allowable value of the SoC, the discharge operation proceeds based on a value twice the error between the nominal voltage and the output voltage, Remaining capacity management device of an energy storage device, characterized in that for calculating an offset voltage that sets the discharge current to 0 when the SoC reaches the minimum allowable value of the SoC.
According to claim 9,
In the fourth operation mode, the y-intercept of the droop curve is formed lower than the output voltage, and when the SoC reaches the maximum allowable value of the SoC, the offset voltage that sets the charging current to 0 is calculated. Remaining energy storage device, characterized in that capacity management device.

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